Water desensitized water work boosters



March 26, 1968 R. DOW ETAL 3,374,736

WATER DESENSITIZEID WATER WORK BOOSTERS Filed Aug. 2, 1966 2Sheets-Sheet 1 Fig.1

INVENTORS RICHARD DOW PAUL E. KELLY PAUL A.

RAMW I i av WNW Y March 26, 1 968 R. DOW ETAL 3,374,736 WATERDESENSITIZED WATER WORK BOOSTERS Filed Aug. 2, 1966 2 Sheets-Sheet 2Fig. 2 ll! 3 L I I l I'-' Fl' 9. 3A

INVENTORS RICHARD DOW PAUL E. KELLY AT RNEY United States Patent E. I.du Pont de Nemours and Company, Wilmington,

Del., a corporation of Delaware Filed Aug. 2, 1966, Ser. No. 569,703 8Claims. (Cl. l0224) ABSTRACT 0F THE DISCLOSURE An explosive boosterwhich is desensitized after exposure to water by ingress of waterthrough at least one aperture in the booster facilitated by a surfactanton at least one surface adjacent said aperture.

Previously, an explosive assembly for use underwater has been providedcomprising an elongated cylindrical shell, a charge of an explosivecomposition within the shell, an elongated cap-well within the shell andembedded in the explosive charge, the cap-well having a tapered upperportion for frictional engagement with the inner surface of the shell, athin film of an adhesive substance between the upper portion of thecap-well and the shell, and a retaining means for an initiator withinthe cap-well. This assembly is described in US. 2,909,121 (to Gernert,Phillippe and Ramsdell). This explosive assembly provides a reliablemeans of detonating blasting agents of a lower order-of-sensitivity in awet or damp environment.

It is sometimes desirable to have a booster which will actuate under wetconditions but after prolonged exposure to water will be desensitized.Prior art boosters have not fulfilled this need. Therefore a need stillexists for a blasting assembly, used in underwater detonation, such asin off-shore seismic exploration, underwater signaling, or underwaterdemolition, of low order-of-sensitivity explosives, which can besuccessfully actuated for a short time, e.g., 2-60 minutes, after beingsubmerged in water but after a more prolonged exposure to water willbecome desensitized so that accidental initiation cannot occur shouldthe assembly misfire and wash ashore.

This invention provides a water work booster 50 constructed that if itshould fail to fire within a designated period of time its explosivecharge will become desensitized by the action of water leakage into anddistribution throughout the explosive component within the booster. Toallow such leakage, at least one aperture is provided in the booster.This is preferably accomplished by providing a cap well with one or moregrooves along the perimeter of its top section, one or more openings atthe base of the cap-well or on its lateral surfaces, and a coating of awetting agent on at least one surface adjacent to the above wateradmission apertures, i.e. the inner and/or outer surfaces of thecap-well, the inner surface of the shell, or the explosive chargeadjacent to the capwell.

The cylindical shell of the explosive assembly, which can be made ofbronze, aluminum, or any other suitable material, contains a charge of aconventionally used, water sensitive detonating explosive adjacent tothe capwell, in an amount normally used for priming or boosting.Examples of water-sensitive explosives includecyclotrimethylenetrinitramine (RDX), pentaerythritol tetranitrate(PETN), 2,4,6-trinitrotoluene (TNT), N-methyl- N,2,4,6-tetranitroaniline(tetryl), or cyclotetramethylenetetranitramine (HMX).

It is this body of explosive which must be desensitized by water inorder to deactivate the booster. To accomplish this a cap-well withrolled edges is provided with an opening, preferably at its baseextremity, and is pressed to a given height within the shell so that itsrolled edges do not form a seal with the shell, and its grooved taperedtop section, while providing a frictional type engagement with the innerwall of the assembly container, allows water to enter, with the aid ofthe wetting agent, into the portion of the shell containing the chargeof detonating explosive. In another typical embodiment of thisinvention, Water leakage into the shell of the booster is accomplishedby using a cap-well, again provided with one or more openings,preferably at its base extremity, which is undersized, thus allowingwater to enter between its outer surface and the inner surface at thebooster shell. Desensitization is then achieved upon absorption of agiven weight percentage of water, this percentage varying with the typeof explosive charge used.

In some embodiments of this invention the capwell can also have holesformed in the lower portion of its lateral walls in place of, or inaddition to, the one at its base. These openings serve to increase therate of water flow into the booster charge. As previously mentioned, atleast one surface adjacent to the water admission apertures, i.e., theinner and/ or outer surfaces of the cap-well, the inner surface of theshell, or the explosive charge, is coated with a wetting agent.Preferably the cap-well, and often the cap-well and one or both of theother surfaces are coated. The coating need not be free of voids anduncoated areas, but preferably provides a substantially continuous pathfor the passage of water to the charge. Wetting agents which can be usedinclude anionic, cationic, nonionic and amphoteric types whose solutiondries to a film. Representative anionic surfactants are alkylarylsulfonates, e.g. sodium alkaylnaphthalene sulfonate, sodium dodecylbenzenesulfonate; hydrocarbon sulfonates, e.g. sodium alkyl sulfonate;alcohol sulfonic esters, e.g. sodium lauryl sulfate, sodium stearylsulfate; aliphatic alcohol phosphates, e.g. sodium alkyl phosphate,alkyl phosphate triethanolamine; aliphatic amide sulfonates, e.g. sodiumstearyl amide methylet-hylsulfonate; alkyl esters of sodiumsulfosuccinic acid, e.g. diamyl ester of sodium sulfosuccinic acid; andsodium dinaphthylmethane disulfonates. Representative cationic surfaceactive agents are substituted amines, e.g. polyalkylene amine,solubilized polyoxyethylene fatty tertiary amine; pyridinium salts, e.g.lauryl pyridinium chloride, lauryl pyridinium bisulfate,tetradecylpyridinium bromide; alkyl ammonium salts, e.g.cetyltrimethylammonium bromide, alkyl dimethyl hydroxyethyl ammoniumbromide, lauryl trimethylammonium chloride; alkyl dimethylamine acetateand substituted imidazoline. Nonionic wetting agents which are typicalof those which can be used are alkylaryl polyether alcohols, fatty acidamine condensates, ethoxylated aliphatic amides, ethoxylated fattyacids, polyethylene glycol ethers, alkylaryl polyglycol ethers, andpolyoxyethylene ethers. Examples of amphoteric wetting agents are fattynitrogen dioarboxylates, long chain betaines, and anhydrous acids ofdicarboxylic coconut derivatives.

It is obvious, therefore, that a choice of one or a combination ofseveral of the variations by which water desensitization can be broughtabout enables the manufacture of a water work booster that can beactuated successfullyafter a certain period of exposure to water,

. ing rolled edges 8, and a hole'7" at its base is pressed A through theopen end of container 6 into the explosive charge 5. A neoprene washer 3is Contained within the cap-well 4 and a rigid washer 2 is inserted overwasher 3. A number of stake crimps 1 are provided in the capwell tosecure the rigid retainer washer 2 and rubbery washer 3 in the properposition at the top of the cap-well.

The explosive charge adjacent to the cap-well within the shell can beany water sensitive material but RDX is preferred in this inventionbecause it is easier to desensitize. The degree of water needed todesensitize the booster depends on the nature of the explosive materialused. For example, desensitization of RDX occurs when 14% moisture isabsorbed by the explosive powder. The typical loadings in this inventionare loose explosive powder over one or two waxed explosive pellets orall loose explosive powder. The preferred loading is two waxed RDXpellets covered by loose RDX powder. In all of the preceding typicalloadings the explosive powder may or may not be coated with a wettingagent, again, depending on the rate of water entry into the explo ivecharge and, therefore, the rate of desensitization that is desired,since the more surface coated the more rapid the desensitization.

The cap-well, in addition to the hole at its base, can also contain aseries of one or more grooves, preferably 4 to 8, along its majorperimeter as shown in FIGURE 1A, which is a top, planar view of thecap-well of FIG- URE 1. Approximately half the normal force fit area isundersized to provide a pathway for fluid to the major body ofexplosive. The grooves are of such depth as to provide a gap of at least5 mils, and preferably 5-20 mils, between the cap-well and the shellwhen the booster is in its assembled state. The hole at the base of thecapwell and/or the holes along its lateral walls are about from 50 milsin diameter to the inner diameter of the base of the cap-well, andpreferably about from 94 to 125 mils, and provide a means of water entryto the explosive. A single hole at the bottom is preferred to a seriesof holes, e.g. 2-6, along the sides for ease of manufacturing usingconventional assembly techniques. The cap-well with a hole at its baseis conveniently pressed into the shell by a press pin so designed thatit plugs the hole in the bottom of the cap-well during pressing and,when a force of approximately 250 to 300 pounds is applied to the pin,it compacts the powder a sufficient amount, i.e. an average density of1.00-1.25 g./cc., so that after the pin is removed the explosive powderwill not fall out through the hole in the cap-well yet when the assemblyis subjected to water the powder will not be so dense as to preventwater entry at the hole. The cap-well preferably is pressed so that thespace between the top of the capwell and the open end of the shell isapproximately 30 to 125 mils, preferably 50-75 mils.

FIGURE 2 is a cross sectional view of another typical embodiment of thisinvention in which 6 designates a generally cylindrical shell containinga charge 5 of detonating explosive in a suitable amount. The cap-well 9is undersized and has its large diameter cut down to an approximateheights of 125 mils. The cap-well 9 is provided with four ratchet-typeretaining points 10 which grip the wall of the booster while the pin iswithdrawn after pressing and which also serve to prevent theloosefitting cap-well 9 from falling out of the booster shell 6. A hole7 is located at the base of the cap-well. A neoprene washer 3 and rigidwasher 2 are contained within the cap-well and are secured in positionby stake crimps 1 as is previously described. The cap-well 9 ispreferably pressed so that the space between the top of the capwell andthe open end of the shell is approximately 500 mils. The cap-well 9 isof an outer diameter such that the open space between it and the innerdiameter of the shell 6 is approximately 5 mils.

A typical press pin for those embodiments of this invention using theundersized cap-well 9 consists of a cylindrical shank, appended to alarger diameter head, whose end is shaped into a conical form, the coneangle being approximately 60, as shown in FIGURE 3. FIGURE 3 is across-sectional view of the press pin in which 12 designates thecylindrical shank, 11 is the layer diameter head, and 13 represents theconically shaped end which plugs the hole in the base of the cap-Wellduring pressing. A similarly designed pin is used to press the groovedcap-well with rolled edges except that the end of the shank consists ofa stepped conical portion as shown in FIGURE 3A which is a detaileddrawing of the point of that press pin. In FIGURE 3A 14 represents atruncated conical section whose cone angle is about 60 from which isappended the conical point 15 whose cone angle is approximately 30. Therest of the press pin is essentlally as shown in FIGURE 3.

The cap-well, shell, or explosive powder, to be coated are rinsed in asolution of wetting agent, e.g. Duponol G (sodium lauryl sulfate), inwater and are allowed to dry thoroughly before the parts are assembled.The solution used to coat the cap-well or shell is a 1-10%, preferably a5%, by volume solution of wetting agent in water and the solution usedto coat the explosive powder is a 0.5-3%, preferably a 1%, by volumesolution of the same.

After the cap-well has been pressed into place, a washer of neoprene orany other rubbery material is placed within the cap-well. This washerhas a central opening of a diameter slightly smallerthan the diameter ofa conventional detonating device, such as a blasting cap. A rigidwasher, of aluminum bronze, or any other suitable material, whosecentral opening is larger than that of the rubbery washer is placed overthe rubbery washer to retain and support the latter. The entire assemblyis then crimped into position at a point immediately above the metalwasher.

The following examples will illustrate the performance of thisinvention.

Example 1 A number of water work boosters are assembled as in FIGURE 2.These boosters are designed to function normally after up to one hourexposure in up to 23 feet of sea water and to become completelydesensitized after 17 hours exposure to 10 feet of sea water. Thetubular shells 6 are made of aluminum and have an outer diameter of 630mils. The shells are previously rinsed in a 5% by volume solution ofDuponol G in water and are allowed to dry thoroughly. The shells 6 areloaded with a charge 5 consisting of two waxed RDX pellets (each 750mils long, 620 mils in diameter and containing 5.25 grams of waxed RDX)over which is loaded 9.0 grams of loose plain, unwaxed RDX powder. Ahole 7 approximately mils in diameter is punched in the center of thebase extremity of an aluminum cap-well 9 which has an undersized majordiameter of 620 mils, the upper portion of the cap-well being 125 milsin height. The cap-well is then treated similarly to the shell 6 byrinsing it in a 5% by volume solution of Duponol G in water and allowingit to dry completely. The cap-well 9 is inserted into the shell and ispressed so that the space between the top of the cap-well and the openend of the shell is approximately 500 mils. The cap-well, beingundersized, fits loosely in the shell thus allowing water to enter inthe void between the cap-well and shell and to reach the explosivematerial. A neoprene washer 3 with a central opening of 260 mils isplaced within the cap-well after pressing is completed and an aluminumwasher 2 whose central opening is 320 mils is placed on top of theneoprene washer. The assembly is then crimped together. The boosters aresubjected to 10 feet of sea water for various lengths of time, the seawater being contained in a steel pipe standing vertically in a 10 footwell. Boosters are tested by attempting actuation thereof afterpredetermined exposures with seismograph instantaneous electric blastingcaps. The results are summarized in the table below.

TABLE 1 Sea Water No. of No. 01 N o. of N o. of Exposure Time DepthTests Detonations Partial Failures (ft.) Detonations 10 11 ll. 0 10 4 3l 0 10 6 1 0 5 10 2 0 8 10 8 1 0 7 10 8 0 0 8 By partial detonation ismeant that some of the loose powder shot but the pellets were notinitiated.

Example 2 of aluminum. These shells 6 are loaded with a charge 5 of twowaxed RDX pellets over which is loaded 9.0 grams of RDX powder treatedwith a 1% solution of Duponol G and allowed to dry completely. Thecapwell 4 has a series of 8 grooves along its major perimeter,approximately half this perimeter being undersized thusly, and a hole 7of 125 mils in diameter punched in A series of 100 boosters, 25 in eachgroup, are assembled and tested similarly as in Example 1 with thefollowing modifications:

In Group 1 an uncoated shell, uncoated cap well and 8.0 grams of coatedpowder are used.

In Group 2 an uncoated shell, coated capwell and 8:0 grams of Coatedpowder are used 90 the approximate center of its base extremity. Thecap- In Group 3 a coated Shell Coated n and SD well is rinsed in a 5% byvolume solution of Duponol grams f uncoated powder are used G in waterand is allowed to dry thoroughly. After in- In Group 4 a coated shell,coated cap-well and 8.0 seftlhgcaprweh 4 n Shell 6, the pis Pressed atgrams f coated powder are d approximately 250 pounds force on thespecial afore- The boosters are subjected to 10 feet of sea water hementioned press pin so that the space between the rolled fore testingand the results are as follows. edges of cap-well 4 and open end ofshell 6 is approxi' TABLE 2' Group 1 Group 2 Group 3 Group 4 ExposureTime D PD F D PD F D PD F D PD F 3 0 2 3 0 2 3 o 2 1 2 2 1 0 4 1 0 4 1 04 3 0 2 1 o 4 o 0 5 0 0 5 o o 5 o 0 5 0 0 5 0 o 5 1 0 4 24hours 1 0 4 00 5 1 0 4 0 0 5 D=number oi detonations, PD=number of partialdetonations, and F=number of failures.

Example 3 mately 65 mils. A neoprene washer 3 and rigid washer 2 40 areinserted and crimped into place by stake crirnps 1 A number of boostersare assem l d nd t d as in as described in Example 1. The boosters arealso tested Example 1 With the exception that the Shell of the blastasdescribed in Example 1. After the boosters withstand ihg assembly is notSubjected to Coating y a Solution of a 24 hour exposure to 10 feet ofsea water and are tested, a wetting agent although the cap-Well is SO cd. These there are four failures out of four trials, indicatingdeboosters are designed to function normaly after up to 5 sensitizationis complete. minutes exposure to 10 feet of sea water, to becomepartially desensitized after up to 30 hours exposure and to Example 5become completely desensitized after 30 hours exposure A number ofboosters are assembled and tested as in to 10 feet of sea water. Theresults are tabulated below. the proceeding example except that 13 gramsof Du- TABLE 3 Sea Water N o. oi N o. of N 0. or No. of Exposure TimeDepth (17.) Tests Detonations Partial Failures Detonatious 10 3 3 o 0 104 3 o 1 10 s 3 1 4 1o 4 o 1 3 For comparative purposes, a number ofboosters are ponol G treated loose RDX powder is used in place ofassembled and tested as described in Example 1 except the 9.0 gramscoated RDX powder and two waxed RDX that no wetting agent is used tocoat any part of the aspellets. After 17 hours exposure to 10 feet ofsea water sembly. Thus the booster consists essentially of a plain thereare five failures out of five trials. cap-well, plain shell, anduncoated RDX powder. The resulting explosive assemblies, after beingexposed to 10 Example 5 feet of sea water for 65 hours have 10detonations out of 10 trials and are, accordingly, not desensitized.Eight boosters are assembled as in Example 4 except 4 that the cap-wellhas a series of 4 grooves along its major Example perimeter instead of 8grooves, the 4 grooves being of A number of boosters are assembled asshown in FIG- such a depth so that half the normal force fit area re-URE 1. These boosters are designed to function normally mainsundersized, 9.0 grams of RDX powder which is after up to 5 minutesexposure to 10 feet of water, after previously treated with a 1%solution of Duponol G which time partial densensitization takes placeuntil after in water is loaded over a wood dowel in place of two 17hours exposure complete densitization occurs. The waxed RDX pellets, anda bronze shell, not treated with tubular shells 6 are 630 mils indiameter and are made a wetting agent, are used. The results aretabulated below.

TABLE 4 Sea Water N0. of No. of No. of N0. of Exposure Time Depth (ft.)Tests Detonations Partial Failures Detonatlons 2 hours 23 2 0 2 4 hours10 2 0 0 2 17 hours. 10 2 0 0 2 24 hours. 10 2 0 0 2 Similar results areobtained in all of the above examples by using other Wetting agents,e.g. sodium stearyl sulfate, sodium dodecylbenzene sulfonate, lauryltrimethylammonium chloride, or polyethylene glycol lauryl ether, inplace of Duponol G.

It can be concluded from the foregoing examples that this novelexplosive assembly provides a water work booster which can be usedreliably underwater to detonate low order-of-sensitivity explosivematerials for a period of 5 minutes to one hour after submergence, butwhich, after a longer exposure to water, will become desensitized thuseliminating the possibility of an accidental actuation should thebooster be Washed ashore.

We claim:

1. In a booster comprising a shell, a cap-well within and in engagementwith said shell, and an explosive charge adjacent to said cap-well, theimprovement which comprises providing at least one aperture in thebooster for admission of water to said explosive charge, and at leastone surface adjacent to said aperture bearing a wetting agent, saidexplosive charge adjacent said aperture being water sensitive.

2. The booster of claim 1, wherein an aperture is provided in the baseof the said cap-well.

3. The booster of claim 2, wherein the outer diameter of the top sectionof said cap-well is at least 10 mils less than the inner diameter ofsaid shell.

4. The booster of claim 2 wherein at least one groove runninglongitudinally through the area of engagement of said shell and cap-wellis provided along the perimeter of the top section of said cap-well.

5. The booster of claim 4 wherein the surface of said cap-well is coatedwith a wetting agent.

6. The booster of claim 4 wherein the inner surface of said shell iscoated with wetting agent.

7. The booster of claim 4 wherein said explosive charge contains wettingagent.

8. The water work booster of claim 4 wherein the surface of saidcap-well, the inner surf-ace of said shell, and said explosive chargeare coated with sodium lauryl sulfonate, said aperture having a diameterof about to mils, and wherein the separation between the said cap-welland said shell in said grooves is about 5 to 20 mils.

References Cited UNITED STATES PATENTS 3,279,372 10/1966 Patterson102-28 3,322,066 5/1967 Grifiith et a1. 102-24 SAMUEL FEINBERG, PrimaryExaminer.

V. R. PENDEGRASS, Assistant Examiner.

